1. Field of the Invention
The present invention relates to a watch equipped with a structure for holding the crown to prevent it from being inadvertently rotated.
2. Description of the Prior Art
In some of watches such as wristwatches, the crown is locked by making use of threaded engagement to prevent inadvertent rotation of the crown during carriage (the structure or function is referred to as threadedly locking, threadedly locking structure, or threadedly locking function in the present specification).
In the threadedly locking structure, a stem pipe is mounted to a barrel in which a watch movement is incorporated. The internal thread of the crown which is fitted over a barrel outside protruding portion is threadedly engaged to an external thread formed on the outer surface of the barrel outside protruding portion of this pipe. In this way, during normal times, the crown is threadedly engaged to the outer surface of the barrel outside protruding portion of the stem pipe such that the crown strikes the barrel outer surface of the barrel. In this way, threadedly locking is achieved, preventing inadvertent rotation of the crown. Also, when the watch movement is manipulated, the crown is threadedly disengaged from the external thread and then the crown is pulled and moved. Under this condition, the stem located inside the stem pipe can be rotationally manipulated via the crown.
In the prior art watch equipped with such threadedly locking structure, the stem pipe mounting portion is generally water-proofed by brazing the stem pipe to the barrel (see, for example, JP-A-57-46181).
Besides, another watch having a stem pipe mounting portion that is water-proofed is also known (see, for example, JP-A-2004-245594). In particular, an external thread different from the external thread to which the crown is threadedly engaged is mounted to the stem pipe. This different external thread is threaded into a pipe installation hole in the barrel. As this threaded insertion is performed, waterproof packing is sandwiched between the barrel and the stem pipe along the direction in which the center axis of the stem pipe extends.
In the watch equipped with the threadedly locking structure, as the crown is repeatedly rotationally manipulated, the internal thread of the crown and the external thread of the stem pipe which are threaded together may wear down or scrape off each other. Consequently, the function of the threadedly locking structure deteriorates.
Where such a circumstance is encountered, parts which are located around the crown and which involve removal of the stem pipe from the barrel cannot be replaced in the watch of JP-A-57-46181 where the stem pipe is brazed to the barrel. Therefore, exchange of the watch outer assembly including the barrel is urged. There is a demand for an improvement of this.
In the watch in which the stem pipe has been threaded into the barrel, it is considered in principle that parts located around the crown including the stem pipe can be exchanged. Even in this structure, however, a rotating force acts on the stem pipe whenever the crown is threaded to, or unthreaded from the stem pipe. This produces rotation of the stem pipe, loosening the threaded engagement of the stem pipe into the barrel. The force at which the waterproof packing is sandwiched decreases. Concomitantly, there is the danger that the waterproofness by the waterproof packing drops.
As a countermeasure against this, adhesive may be loaded into the threaded portion between the stem pipe and the barrel. Where adhesive bonding is done in this way, it is difficult to remove the stem pipe from the barrel. Practically, it is impossible to replace parts located around the crown. As a result, where the threadedly locking function deteriorates, it is urged to replace the watch outer assembly including the barrel. Therefore, there is a demand for an improvement of this.
It is an object of the present invention to provide a watch in which the waterproofness will not be impaired by manipulation of the crown and which permits exchange of parts located around the crown in a case where the threadedly locking function has deteriorated.